Make _.escapeRegExp escape characters that could cause problems for escape sequences and other edge cases.

lodash.src.js

@@ -97,7 +97,7 @@
    * Used to match `RegExp` [syntax characters](http://ecma-international.org/ecma-262/6.0/#sec-patterns)
    * and those outlined by [`EscapeRegExpPattern`](http://ecma-international.org/ecma-262/6.0/#sec-escaperegexppattern).
    */
-  var reRegExpChars = /[\/^$\\.*+?()[\]{}|\n\r\u2028\u2029]/g,
+  var reRegExpChars = /^[:!,]|[\/^$\\.*+?()[\]{}|]|(^[0-9a-fA-Fnrtuvx])|([\n\r\u2028\u2029])/g,
       reHasRegExpChars = RegExp(reRegExpChars.source);
 
   /** Used to match [combining diacritical marks](https://en.wikipedia.org/wiki/Combining_Diacritical_Marks). */
@@ -233,6 +233,15 @@
     'object': true
   };
 
+  /** Used to escape characters for inclusion in compiled regexes. */
+  var regexpEscapes = {
+    '0': 'x30', '1': 'x31', '2': 'x32', '3': 'x33', '4': 'x34',
+    '5': 'x35', '6': 'x36', '7': 'x37', '8': 'x38', '9': 'x39',
+    'A': 'x41', 'B': 'x42', 'C': 'x43', 'D': 'x44', 'E': 'x45', 'F': 'x46',
+    'a': 'x61', 'b': 'x62', 'c': 'x63', 'd': 'x64', 'e': 'x65', 'f': 'x66',
+    'n': 'x6e', 'r': 'x72', 't': 'x74', 'u': 'x75', 'v': 'x76', 'x': 'x78'
+  };
+
   /** Used to escape characters for inclusion in compiled string literals. */
   var stringEscapes = {
     '\\': '\\',
@@ -489,15 +498,32 @@
   }
 
   /**
-   * Used by `_.template` to escape characters for inclusion in compiled
-   * string literals.
+   * Used by `_.escapeRegExp` to escape characters for inclusion in compiled regexes.
+   *
+   * @private
+   * @param {string} chr The matched character to escape.
+   * @param {string} leadingChar The capture group for a leading character.
+   * @param {string} whitespaceChar The capture group for a whitespace character.
+   * @returns {string} Returns the escaped character.
+   */
+  function escapeRegExpChar(chr, leadingChar, whitespaceChar) {
+    if (leadingChar) {
+      chr = regexpEscapes[chr];
+    } else if (whitespaceChar) {
+      chr = stringEscapes[chr];
+    }
+    return '\\' + chr;
+  }
+
+  /**
+   * Used by `_.template` to escape characters for inclusion in compiled string literals.
    *
    * @private
    * @param {string} chr The matched character to escape.
    * @returns {string} Returns the escaped character.
    */
   function escapeStringChar(chr) {
-    return '\\' + (stringEscapes[chr] || chr);
+    return '\\' + stringEscapes[chr];
   }
 
   /**
@@ -10521,7 +10547,7 @@
     function escapeRegExp(string) {
       string = baseToString(string);
       return (string && reHasRegExpChars.test(string))
-        ? string.replace(reRegExpChars, escapeStringChar)
+        ? string.replace(reRegExpChars, escapeRegExpChar)
         : (string || '(?:)');
     }
 

test/test.js

@@ -285,6 +285,15 @@
     new URIError
   ];
 
+  /** Used to check escaped regexp characters. */
+  var regexpEscapes = {
+    '0': 'x30', '1': 'x31', '2': 'x32', '3': 'x33', '4': 'x34',
+    '5': 'x35', '6': 'x36', '7': 'x37', '8': 'x38', '9': 'x39',
+    'A': 'x41', 'B': 'x42', 'C': 'x43', 'D': 'x44', 'E': 'x45', 'F': 'x46',
+    'a': 'x61', 'b': 'x62', 'c': 'x63', 'd': 'x64', 'e': 'x65', 'f': 'x66',
+    'n': 'x6e', 'r': 'x72', 't': 'x74', 'u': 'x75', 'v': 'x76', 'x': 'x78'
+  };
+
   /** Used to check problem JScript properties (a.k.a. the `[[DontEnum]]` bug). */
   var shadowProps = [
     'constructor',
@@ -4270,14 +4279,39 @@
       strictEqual(_.escapeRegExp(unescaped + unescaped), escaped + escaped);
     });
 
-    test('should handle strings with nothing to escape', 1, function() {
-      strictEqual(_.escapeRegExp('abc'), 'abc');
+    test('should escape special characters at the start of a string', 1, function() {
+      var chars = [
+        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+        'a', 'b', 'c', 'd', 'e', 'f',
+        'A', 'B', 'C', 'D', 'E', 'F',
+        'n', 'r', 't', 'u', 'v', 'x',
+        ':', '!', ','
+      ];
+
+      var expected = _.map(chars, function(chr) {
+        return ['\\' + (regexpEscapes[chr] || chr) + 'z', 'z' + chr];
+      });
+
+      var actual = _.map(chars, function(chr) {
+        return [_.escapeRegExp(chr + 'z'), _.escapeRegExp('z' + chr)];
+      });
+
+      deepEqual(actual, expected);
     });
 
-    test('should return `"(?:)"` when provided nullish or empty string values', 3, function() {
-      strictEqual(_.escapeRegExp(null), '(?:)');
-      strictEqual(_.escapeRegExp(undefined), '(?:)');
-      strictEqual(_.escapeRegExp(''), '(?:)');
+    test('should handle strings with nothing to escape', 1, function() {
+      strictEqual(_.escapeRegExp('ghi'), 'ghi');
+    });
+
+    test('should return `"(?:)"` when provided nullish or empty string values', 1, function() {
+      var values = [, null, undefined, ''],
+          expected = _.map(values, _.constant('(?:)'));
+
+      var actual = _.map(values, function(value, index) {
+        return index ? _.escapeRegExp(value) : _.escapeRegExp();
+      });
+
+      deepEqual(actual, expected);
     });
 
     test('should work with `eval` and `Function`', 2, function() {